This invention relates generally to cathode ray tubes (CRTs) and more particularly to a tension mask assembly having a vibration damper applied to an area of the tension mask.
A color cathode ray tube, or CRT, includes an electron gun for forming and directing three electron beams to a screen of the tube. The screen is located on the inner surface of the faceplate panel of the tube and is made up of an array of elements of three different color-emitting phosphors. A shadow mask, which may be either a formed mask or a tension mask having strands, is located between the electron gun and the screen. The electron beams emitted from the electron gun pass through apertures in the shadow mask and strike the screen causing the phosphors to emit light so that an image is displayed on the viewing surface of the faceplate panel.
One type of CRT has a tension mask comprising a set of strands that are tensioned onto a mask support frame to reduce their propensity to vibrate at large amplitudes under external excitation. Such vibrations would cause gross electron beam misregister on the screen and would result in objectionable image anomalies to the viewer of the CRT.
One method of tensioning a mask utilizes a mask support frame having a pair of support blade members mounted on opposite sides of the frame parallel to the major axis of the tension mask. The tension mask extends between the support blade members and is held in tension to reduce its propensity to vibrate. A problem exists in that the support blade members supporting the mask are subject to vibration relative to the frame when external vibration or microphonic vibration is applied to the frame. Such external vibrations may then be undesirably transferred to the tension mask.
The invention provides a CRT having a tension mask and a vibration damper to receive vibration from the tension mask. The tension mask is attached to a support frame, wherein the support frame has longs sides (22, 24) parallel to a major axis and shorts sides parallel to a minor axis (26, 28). The tension mask includes borders which are near the short sides and parallel therewith. The vibration damper comprises an elongated strip member having first and second ends mounted at respective attachment locations along the border and a major portion which is in frictional contact with the border.